If I get ride of Cable channels and just keep basic cable, will I still be able to get all of the Roku channels I'm getting now. I just start with Roku.
The short answer is yes, but Roku has deliberately tried to confuse people with the term "channel". "Channel" may mean "app" or it may mean a "channel" within an app. Any app you have on your Home Screen will still be available, but some require a cable/satellite subscription. "Channels" within The Roku Channel that aren't premium channels will still be available. I'm sorry if I've just made it more confusing, but blame Roku for that.
I would expect any channel for which you have 1: authenticated via your cable package, and 2: is part of the channels dropped by your switch to the lower package, to also become unavailable on Roku. That is to say the content providers know that trick.
Or to put it another way: for each channel you have on Roku, look it up in the channel store and see whether it says something like “CABLE OR SATELLITE SUBSCRIPTION REQUIRED” or “Sign in with your TV subscription to gain access to the entire catalog of on demand & live content.” If you see any language like that, you can expect to lose some or all of that content if the corresponding channel is dropped from cable.